Add some labels for Elastic

program/localization/en_US/labels.inc

@@ -330,6 +330,8 @@ $labels['alwaysshow'] = 'Always show images from $sender';
 $labels['alwaysallow'] = 'Always allow from $sender';
 $labels['isdraft']    = 'This is a draft message.';
 $labels['andnmore']   = '$nr more...';
+$labels['headers']    = 'Headers';
+$labels['envelope']   = 'Envelope';
 $labels['togglemoreheaders'] = 'Show more message headers';
 $labels['togglefullheaders'] = 'Toggle raw message headers';